Reclosable packages are widely used in the packaging of a variety of products, especially food. Reclosable packages are very convenient because, after initially opening a reclosable package, consumers can reclose the package and better preserve the contents of the package. A top film and a bottom film enclose the contents of the package by heat sealing the top film and the bottom film together along the sides of the films. A side of the top film and the bottom film remain unsealed. A reclosable profile strip is sealed along the unsealed side of the top film and the bottom film, forming a reclosable package.
The reclosable profile strip on the reclosable package has a top web and a bottom web. The reclosable profile strip forms a reclosable package by sealing the bottom web to the bottom film and by sealing the top web to the top film. The top web and the bottom web each has an interlocking member. The interlocking member of the top web interlocks with the interlocking member of the bottom web, usually as a mated pair of a male profile and a female profile. In this way, the consumer can reclose the package by interlocking the interlocking members of the top web and the bottom web.
A common method of producing recloseable packages is by the horizontal form-fill-seal method. Vacuum packaging machines such as the TIROMAT machinery incorporate the horizontal form-fill-seal method. A horizontal form-fill-seal machine requires an already-made continuous roll of recloseable profile strip. The recloseable profile strips presently used with the horizontal form-fill-seal machinery are formed from a molten material. The reclosable profile strip is extruded through a die from the molten material into three separate sections. Two top webs each having an interlocking member are extruded alongside and at opposite ends of a bottom web having two interlocking members. The two top webs and the bottom web are then cooled. After cooling, the two top webs are positioned above the bottom web, and a "mater" interlocks the interlocking members of the top webs with the interlocking members of the bottom web. The continuous recloseable profile strip forms a roll of double recloseable profile strip because the two pairs of interlocking members will form the recloseable profile strips of two recloseable packages.
A horizontal form-fill-seal machine receives a continuous, double recloseable profile strip from a roll along with a continuous sheet of bottom film from another roll. The recloseable profile strip is positioned above the bottom film. In the first stage of the method as described in U.S. Pat. No. 4,969,309 and incorporated here by reference, the machine forms loops in the bottom web perpendicular to the profile strip. Heating bars bond the bottom web of the recloseable profile strip to the bottom film, and a pair of heating rods also bond or "tack" seal the top webs of the profile strip to the bottom web. The machine cuts the continuous, double recloseable profile strip into sections of double recloseable profile strip such that each section of recloseable profile strip corresponds to a pair of recloseable packages. The "tack" seals prevent the top webs of each section of recloseable profile strip from slipping with respect to the bottom web, resulting in a detective recloseable package. The machine then straightens the bottom film, leaving gaps between the sections of recloseable profile strip.
After the first stage, the horizontal form-fill-seal machine has sections of double recloseable profile strip bonded to the bottom film. In the remaining stages, the machine first preheats the bottom film and forms a cavity in the shape of the eventual contents of the package. The machine then fills the cavity with the product. The filled cavity is covered by a top film and heat sealed to the bottom film and the recloseable profile strip, forming a filled recloseable package. At this time, heating bars may activate bonding material located on opposing portions of the top webs and the bottom web to form peel seals between the top webs and the bottom web that remain sealed until the package is initially opened. Finally, the machine forms individual packages by cutting the bottom film and the bottom web of the double recloseable profile strip along the length of the bottom web and by cutting the top film and the bottom film of the package outside of the heat seal that joins them.
The tack seals of the first stage are necessary to prevent the slipping of the top webs from the bottom web, resulting in a defective recloseable package. The tack seals, however, create other problems with the recloseable packages formed by horizontal form-fill-seal machinery. The tack seals can melt the interlocking members of the top webs and the bottom web together and, thus, hinder the opening of the recloseable package. Similarly, if the bonding material for peel seals is present, the tack seals may inadvertantly activate the bonding material, and when the machine intentionally activates the bonding material, the doubly activated bonding material forms highly aggressive peel seals. These highly aggressive peel seals also hinder the opening of the recloseable package. The application of a tack seal requires heating rods to crush the top webs and the bottom web together. Sometimes, these heating rods puncture the bottom film, the top film or the bottom film. A puncture leads to a defective package and a spoiled or contaminated product.